Sacrificial oxide must be etched out of surface micromachined devices
to release the mechanical structures. The drying procedure is
critical if stiction is to be minimized.
www links to research on stiction free release:
This is the MCNC procedure for etching 2 micron thick PSG layers with a minimum of 30 microns between release holes.
If the dice are coated with photoresist for protection in sawing,
strip it by soaking in acetone for 20 minutes; mildly agitation is helpful.
Note: ACT is an alternative to acetone as a stripper, but it will
attack any copper layers.
Rinse in isopropanol for one minute, then in DI water.
Etch the PSG in fully concentrated (49%) HF at room temperature for
2.5 minutes, with gentle agitation.
Quickly transfer to DI water and rinse for 10 minutes
Quickly transfer to isopropyl alcohol for a 5 minute rinse.
Remove from methanol and IMMEDIATELY bake for 10-15 minutes at 110C.